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      LFS Target Architectures
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      <h4>
        Linux From Scratch - Version 8.0
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      <h3>
        Preface
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      <h1 class="sect1">
        <a id="pre-architecture" name="pre-architecture"></a>iii. LFS Target
        Architectures
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      <p>
        The primary target architectures of LFS are the AMD/Intel x86
        (32-bit) and x86_64 (64-bit) CPUs. On the other hand, the
        instructions in this book are also known to work, with some
        modifications, with the Power PC and ARM CPUs. To build a system that
        utilizes one of these CPUs, the main prerequisite, in addition to
        those on the next few pages, is an existing Linux system such as an
        earlier LFS installation, Ubuntu, Red Hat/Fedora, SuSE, or other
        distribution that targets the architecture that you have. Also note
        that a 32-bit distribution can be installed and used as a host system
        on a 64-bit AMD/Intel computer.
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      <p>
        Some other facts about 64-bit systems need to be added here. When
        compared to a 32-bit system, the sizes of executable programs are
        slightly larger and the execution speeds are only slightly faster.
        For example, in a test build of LFS-6.5 on a Core2Duo CPU based
        system, the following statistics were measured:
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<code class="computeroutput">Architecture Build Time     Build Size
32-bit       198.5 minutes  648 MB
64-bit       190.6 minutes  709 MB</code>
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      <p>
        As you can see, the 64-bit build is only 4% faster and is 9% larger
        than the 32-bit build. The gain from going to a 64-bit system is
        relatively minimal. Of course, if you have more than 4GB of RAM or
        want to manipulate data that exceeds 4GB, the advantages of a 64-bit
        system are substantial.
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      <p>
        The default 64-bit build that results from LFS is considered a "pure"
        64-bit system. That is, it supports 64-bit executables only. Building
        a "multi-lib" system requires compiling many applications twice, once
        for a 32-bit system and once for a 64-bit system. This is not
        directly supported in LFS because it would interfere with the
        educational objective of providing the instructions needed for a
        straightforward base Linux system. You can refer to the <a class=
        "ulink" href="http://trac.clfs.org/">Cross Linux From Scratch</a>
        project for this advanced topic.
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